Despite recent advances in behavior and pharmacological smoking cessation technologies, relapse is still the most predictable event following a smoking cessation attempt. In general, the cognitive-behavioral intervention programs have concentrated on preventing relapse by developing subjects' skills to resume abstinence following a slip. However, long-term abstinence rates are not terribly impressive nor have they significantly improved over the past 20 years. Recent research has focused on the analysis of the slip or isolated smoking lapse and its importance to subsequent relapse suggesting that the prevention of a slip may improve long-term abstinence rates. New, innovative and aggressive technologies are needed to focus on prevention of the initial slip, rather than rescuing recently abstinent smokers from the detrimental impact of such slips. A contingency management approach is particularly well-suited to the challenge of attaining continuous abstinence because of the opportunity to reinforce very specific, discrete and easily measured target behaviors. The present series of studies will test and refine the behavioral technique of contingent reinforcement as a means of improving rates of continuous abstinence in motivated quitters, with an emphasis on recruitment of dependent low income smokers. Unique to the study will be the biochemical measurement of continuous abstinence over 4-12 weeks in an attempt to quantify the duration of continuous abstinence and the detection of lapses. Study hypotheses will address the efficacy of contingent incentives on duration of continuous abstinence during the first 30 days post-cessation (Study 1), the effects of reinforcing continuous versus point-in-time abstinence (Study 2), the relapse prevention efficacy of extending contingent incentives over a more prolonged (3-month) post-cessation time (Study 3), and the efficacy of a contingent incentive protocol in medically high risk smokers (Study 4). In all studies, psychosocial (stress and anxiety), motivational and demographic characteristics will be assessed in relation to continuous abstinence and lapses. Overall, this project will provide valuable new information about the clinical effectiveness of a therapy intervention that offers tangible reinforcement for continuous abstinence. Reinforcement for abstinence has been previously shown successful for promoting reduction and temporary cessation in smokers and for promoting continuous abstinence in cocaine abusers. These studies will extend the clinical generality of this promising approach by determining its utility in heavy smokers and offer new findings concerning smokers with medical risks. The studies will have both scientific and public health importance.